Hair is an exceedingly strong fiber. This strength is conferred primarily by disulfide bonds within the cortex of the hair fiber and by a profective cuticle layer that encapsulates the entire hair fiber. The natural degree of curliness of one's hair is largely determined by the orientation of these disulfide bonds. In order to change the physical configuration of hair, these disulfide bonds must be broken. When hair is exceedingly curly in its natural state, fairly aggressive conditions must normally be used to substantially lessen or eliminate the amount of curl. Simply put, the curlier the hair, the more curl that needs to be removed to make the hair straight and, in turn, the more disulfide bonds need to be broken to make the hair straight.
In order to straighten exceedingly curly hair, alkaline compositions must be used. These compositions differ from the thiol-based compositions used in perming in that bond breakage is achieved by hydroxide-containing compounds. Hydroxides are very strong reducing agents and the compositions in which they are formulated are highly alkaline. Accordingly, the pH of relaxer compositions is generally within the range of pH 12 to pH 14. In most circumstances, compositions for the straightening of exceedingly curly hair are termed “lye” type and “no-lye” type compositions. The relaxing process is usually combined with mechanical straightening of the hair, such as by combing, where straightening occurs through changing of the relative positions of opposite polypeptide chains.
As would be understood by one of ordinary skill in the art, under strongly alkaline conditions, such as those conferred by the application of typical relaxer compositions to hair, the disulfide bonds of cystine in hair are converted to stable, irreversible crosslinks of primarily lanthionine with some lysinoalanine. Thus, unlike when hair is reduced with thiol or bisulfite relaxers, a chemical oxidative re-linking step is unnecessary. Rather, the only step required following an alkaline relaxer is to promptly remove the relaxing composition by rinsing the hair with water, and to substantially neutralize all remaining alkaline material to avoid damage to the hair protein or skin. For this purpose, a neutral pH or acidic pH shampoo is applied to the hair to neutralize and remove residual alkaline material from the hair and scalp.
In use, after rinsing the hair of most of the excess relaxer composition, the shampoo neutralizer is applied to the hair. In order to make sure that substantially all of the alkalinity is removed from the hair, care must be taken to fully distribute the shampoo neutralizer through the hair. As such, existing methods of neutralizing relaxed hair invariably require the neutralizer shampoo composition to be massaged or kneaded into the relaxed hair.
However, when hair is in its relaxed state i.e., after straightening but before the alkalinity is removed, the fibers are easily stretched, twisted, or broken. Those skilled in the art will recognize that the studies given in the current literature clearly demonstrate that chemical treatments such as bleaching, waving, and straightening cause changes in the physical properties of hair and related fibers. Measurements of parameters such as Young's Modulus, Load-Elongation Curves and the like have shown that: (1) wet hair stretches more easily than dry hair; (2) chemically treated hair loses some of its tensile strength; (3) the amount of force required to stretch a wet chemically treated hair is lower than that required to stretch a wet, non-treated hair to the same extent; and (4) the amount of total force required to reach the breaking point in a wet, chemically treated hair is lower than that required to reach the point of breakage in wet, non-treated hair. Excessive stretching can also result in cuticle lifting and fiber splitting.
The elliptical shape of hair fibers of people of African descent, so-called “kinky” or “curly” hair is also well documented in the literature. Hair of this type tends to have a combination of areas of fairly normal cross-sectional area with intermittent bends and twists where the cross-sectional area of the hair fiber is reduced or narrowed. These areas of reduced cross-sectional area in effect create natural weak spots where mechanical forces applied to the hair are concentrated over a smaller area. Thus, persons with this type of hair are inherently more at risk of hair damage by mechanical forces applied to the hair fiber than are persons with hair of more uniform cross-sectional area. Further, excessive stretching and twisting can result in damage to or loss of hair's profective cuticle leaving the hair vulnerable to damage from heat styling, combing, and environmental effects of natural weathering. Accordingly, when a shampoo neutralizer is massaged or kneaded into the relaxed hair, hair breakage necessarily results because of the application of force to the relaxed hair from the massaging or kneading of the neutralizer shampoo into the hair. Such breakage, which may be considerable, normally occurs even when the operator is exercising care in applying the shampoo neutralizer to the relaxed hair.
Because of the significant damage resulting from the relaxation of hair, care must be taken in subsequent hair treatments. In particular, it is generally not recommended to color relaxed hair on the same day or even in the same week as the relaxer process. This is due, in part, to the fact that hair colorants are generally applied from an alkaline composition, such as those that contain ammonia or other similar materials. Such materials are generally added to colorant compositions to swell the hair and improve the penetration of the colorant into the hair fiber.
As shown in the Comparative Examples of this application and as anecdotally known to one of ordinary skill in the art, in prior art methods of neutralizing relaxed hair, the hair retains a significant amount of alkalinity even after several shampoo neutralization steps. Therefore, it is not surprising that the application of an alkaline colorant product to an alkaline hair fiber can exacerbate damage to the hair from relaxers.
Further, even when a hair color is not applied from a highly alkaline composition, the mere fact that hair relaxed and neutralized with prior art methods of neutralization retains alkalinity makes same day (or even same week) coloration substantially undesirable. For example, the additional manipulation of hair that retains alkalinity due to relaxing can cause significant breakage of the hair. Further, alkaline hair generally is more porous and less likely to retain color. Colorants generally work by absorption of the colorant moiety into the hair. If the hair is porous (as by swelling caused by excess alkalinity), the colorant will be more likely to leach from the hair after application of the color, thus leading to color loss. This color loss is, of course, undesirable. Since the alkalinity of relaxed hair will usually decrease somewhat over time, it is generally believed that it is better to not to color hair within a short time after it is relaxed, but rather wait until the relaxed hair equillabrates.
In light of the above, it would be desirable to have a process for neutralizing relaxed hair that minimizes or substantially eliminates the chance of hair damage during neutralization. Further, it would be desirable to have a process where effective neutralization of reduced hair is conferred without having to substantially manipulate the hair to apply the neutralizer composition. Still further, it would be desirable to have hair that is less damaged after relaxing and neutralizing hair. Additionally, not being able to color hair on the same day that it is relaxed is inconvenient for the customer because multiple visits to the salon are necessary to obtain the desired result. It would therefore be desirable to have the ability to relax and color hair at approximately the same time without causing significant hair damage, while also providing a satisfactory coloring process.